Fri·Mar 29, 2019Friday·March 29, 2019

1. 01*

   Structure functions at small x from world-lines. I: Unpolarized distributions

   Andrey Tarasov🇺🇸 · Raju Venugopalan🇺🇸

   The world-line representation of quantum field theory is a powerful framework for the computation of perturbative multi-leg Feynman amplitudes. In particular, in gauge theories, it provides an efficient way, via point particle Grassmann functional integrals, to compute spinor and color traces in these amplitudes. Further, semi-classical approximations to quantum mechanical world-line trajectories provide useful intuition in a wide range of dynamical problems. We develop here the world-line approach to compute deeply inelastic structure functions in the small x Regge limit of QCD. In particular, in a shockwave approximation valid in this limit, we show how one recovers the well-known dipole model for unpolarized structure functions. In a follow-up work, we will discuss the world-line computation of polarized structure functions at small x.

   hep-phhep-thnucl-thPRD(2019)·17 citations
2. 02*

   Chiral Estimate of QCD Pseudocritical Line

   K. Zarembo🇸🇪

   Relatively low crossover temperature suggests that chiral symmetry restoration in QCD may well be described within the low-energy effective theory. The shape of the pseudocritical line in the T-mu plane is estimated within this assumption. No critical endpoint is found for physical values of quark masses.

   hep-phhep-lathep-thJETP Lett.(2019)·1 citation
3. 03*

   A 96 GeV Higgs Boson in the N2HDM

   T. Biekötter🇪🇸 · M. Chakraborti🇪🇸 · S. Heinemeyer🇪🇸

   We discuss a $\sim 3\sigma$ signal (local) in the light Higgs-boson search in the diphoton decay mode at $\sim 96$ GeV as reported by CMS, together with a $\sim 2\sigma$ excess (local) in the $b\bar{b}$ final state at LEP in the same mass range. We interpret this possible signal as a Higgs boson in the 2 Higgs Doublet Model with an additional real Higgs singlet (N2HDM). We find that the lightest Higgs boson of the N2HDM can perfectly fit both excesses simultaneously, while the second lightest state is in full agreement with the Higgs-boson measurements at 125 GeV, and the full Higgs-boson sector is in agreement with all Higgs exclusion bounds from LEP, the Tevatron and the LHC as well as other theoretical and experimental constraints. We show that only the N2HDM type II and IV can fit both the LEP excess and the CMS excess with a large ggF production component at $\sim 96$ GeV. We derive bounds on the N2HDM Higgs sector from a fit to both excesses and describe how this signal can be further analyzed at the LHC and at future $e^{+}{e}^{-}$ colliders, such as the ILC.

   hep-phhep-exEPJC(2020)·137 citations
4. 04*

   Natural supersymmetric Twin Higgs

   Marcin Badziak🇵🇱 · Keisuke Harigaya🇺🇸

   A new class of supersymmetric Twin Higgs (TH) models where new gauge symmetry is responsible for the TH mechanism is reviewed. In this class of models the Higgs mass is naturally in agreement with the LHC measurement while the electroweak symmetry breaking is realised without excessive tuning despite of strong lower bounds on masses of supersymmetric particles set by the LHC. Assuming particular non-abelian structure of the new gauge symmetry the model remains perturbative up to the energy scale of gravity, in contrast to all previously proposed UV completions of the TH model.

   hep-phJ.Phys.Conf.Ser.(2020)·2 citations
5. 05*

   Roberge-Weiss periodicity, canonical sector and modified Polyakov-loop

   Kouji Kashiwa🇯🇵 · Hiroaki Kouno🇯🇵

   To obtain deeper understanding of QCD properties at finite temperature, we consider the Fourier decomposition of the grand-canonical partition function based on the canonical ensemble method via the imaginary chemical potential. Expectation values are, then, represented by summation over each canonical sector. We point out that the modified Polyakov-loop can play an important role in the canonical ensemble; for example, the Polyakov-loop paradox which is known in the canonical ensemble method can be evaded by considering the quantity. In addition, based on the periodicity issue of the modified Polyakov-loop at finite imaginary chemical potential, we can construct the systematic way to compute the dual quark condensate which has strong unclearness in its foundation in the presence of dynamical quarks so far.

   hep-phhep-lathep-thPRD(2019)·6 citations
6. 06*

   Note on a solution to domain wall problem with the Lazarides-Shafi mechanism in axion dark matter models

   Chandrasekhar Chatterjee🇯🇵 · Tetsutaro Higaki🇯🇵 · Muneto Nitta🇯🇵

   Axion is a promising candidate of dark matter. After the Peccei-Quinn symmetry breaking, axion strings are formed and attached by domain walls when the temperature of the universe becomes comparable to the QCD scale. Such objects can cause cosmological disasters if they are long-lived. As a solution for it, the Lazarides-Shafi mechanism is often discussed through introduction of a new non-Abelian (gauge) symmetry. We study this mechanism in detail and show configuration of strings and walls. Even if Abelian axion strings with a domain wall number greater than one are formed in the early universe, each of them is split into multiple Alice axion strings due to a repulsive force between the Alice strings even without domain wall. When domain walls are formed as the universe cools down, a single Alice string can be attached by a single wall because a vacuum is connected by a non-Abelian rotation without changing energy. Even if an Abelian axion string attached by domain walls are created due to the Kibble Zurek mechanism at the chiral phase transition, such strings are also similarly split into multiple Alice strings attached by walls in the presence of the domain wall tension. Such walls do not form stable networks since they collapse by the tension of the walls, emitting axions.

   hep-phastro-ph.COhep-thPRD(2020)·22 citations
7. 07*

   Study of $P_c(4457)$, $P_c(4440)$, and $P_c(4312)$ in a quasipotential Bethe-Salpeter equation approach

   Jun He🇨🇳

   Very recently, the LHCb Collaboration reported their new results about the pentaquarks at charm energy region. Based on the new experimental results, we recalculate the molecular states composed of a ${\Sigma }_c^{(\ast )}$ baryon and a ${\bar{D}}^{(\ast )}$ meson in a quasipotential Bethe-Salpeter equation approach. The two-peak structure around 4450 MeV can be interpreted as two ${\Sigma }_c{\bar{D}}^{\ast }$ bound states with spin parities $1/2^{-}$ and $3/2^{-}$. The newly observed pentaquark $P_c(4312)$ can be assigned as a ${\Sigma }_c\bar{D}$ bound state with spin parity $1/2^{-}$. The experimental determination of spin parities will be very helpful to understand the internal structure of these pentaquarks.

   hep-phnucl-thEPJC(2019)·209 citations
8. 08*

   BSM Matter providing Neutrino Masses and Gauge Unification

   Ivica Picek🇭🇷

   I present several scenarios developed in Zagreb, in which TeV-scale particles belonging to non-trivial weak-isospin multiplets give rise to neutrino-mass mechanisms different from conventional type I, II and III seesaw models. Two dim 9 tree-level mechanisms, presented first, provide an appealing testability of their exotic TeV-scale particles at the LHC. These models are not genuine, since their particles also provide competing dim 5 loop contributions. The loop-models presented next are genuine, without competing tree-level contributions. Among them, the three-loop model involves high-order weak multiplets leading to Landau poles. The one-loop model with scalar triplet as the largest multiplet, in addition to good UV properties, provides the particle set promising for gauge coupling unification. Therefore, it served us as a starting point for a study of SU(5) embedding of additional particles leading to viable unification scenarios. To distinguish among them begs for additional principle which reigns over particle completion and eventual dark matter considerations.

   hep-ph1 citation
9. 09*

   Nucleon Structure from Lattice QCD Calculations

   Jian-Wei Qiu🇺🇸

   Parton distribution and correlation functions describe the relation between a hadron and the quarks and gluons (or collectively, the partons) within it, and carry rich information on hadron's partonic structure that cannot be calculated by QCD perturbation theory. In this talk, I will review what lattice QCD can and cannot do for calculating the parton distribution and correlation functions, and the new ideas and efforts around the world to explore nucleon structure from lattice QCD calculations by combining the strength of both lattice QCD and perturbative QCD in such a way that is complementary to our on-going effort to extract these fundamental functions from experimental data.

   hep-phhep-latnucl-thJPS Conf.Proc.(2019)·2 citations
10. 10*

    ${\Lambda }_b$ decays into ${\Lambda }_c^{\ast }\ell {\bar{\nu }}_{\ell }$ and ${\Lambda }_c^{\ast }{\pi }^{-}$ $[{\Lambda }_c^{\ast }={\Lambda }_c(2595)$ \& ${\Lambda }_c(2625)]$ and heavy quark spin symmetry

    J. Nieves🇪🇸 · R. Pavao🇪🇸 · S. Sakai🇨🇳

    We study the implications for ${\Lambda }_b\to {\Lambda }_c^{\ast }\ell {\bar{\nu }}_{\ell }$ and ${\Lambda }_b\to {\Lambda }_c^{\ast }{\pi }^{-}$ $[{\Lambda }_c^{\ast }={\Lambda }_c(2595)$ and ${\Lambda }_c(2625)]$ decays that can be deduced from heavy quark spin symmetry (HQSS). Identifying the odd parity ${\Lambda }_c(2595)$ and ${\Lambda }_c(2625)$ resonances as HQSS partners, with total angular momentum--parity $j_q^P=1^{-}$ for the light degrees of freedom, we find that the ratios $\Gamma ({\Lambda }_b\to {\Lambda }_c(2595){\pi }^{-})/\Gamma ({\Lambda }_b\to {\Lambda }_c(2625){\pi }^{-})$ and $\Gamma ({\Lambda }_b\to {\Lambda }_c(2595)\ell {\bar{\nu }}_{\ell })/\Gamma ({\Lambda }_b\to {\Lambda }_c(2625)\ell {\bar{\nu }}_{\ell })$ agree, within errors, with the experimental values given in the Review of Particle Physics. We discuss how future, and more precise, measurements of the above branching fractions could be used to shed light into the inner HQSS structure of the narrow ${\Lambda }_c(2595)$ odd-parity resonance. Namely, we show that such studies would constrain the existence of a sizable $j_q^P=0^{-}$ component in its wave-function, and/or of a two-pole pattern, in analogy to the case of the similar $\Lambda (1405)$ resonance in the strange sector, as suggested by most of the approaches that describe the ${\Lambda }_c(2595)$ as a hadron molecule. We also investigate the lepton flavor universality ratios $R[{\Lambda }_c^{\ast }]=\mathcal{B}({\Lambda }_b\to {\Lambda }_c^{\ast }\tau {\bar{\nu }}_{\tau })/\mathcal{B}({\Lambda }_b\to {\Lambda }_c^{\ast }\mu {\bar{\nu }}_{\mu })$, and discuss how $R[{\Lambda }_c(2595)]$ may be affected by a new source of potentially large systematic errors if there are two ${\Lambda }_c(2595)$ poles.

    hep-phEPJC(2019)·19 citations
11. 11*

    Probing new physics with displaced vertices: muon tracker at CMS

    Kyrylo Bondarenko🇳🇱 · Alexey Boyarsky🇳🇱 · Maksym Ovchynnikov🇳🇱 · Oleg Ruchayskiy🇩🇰 · Lesya Shchutska🇨🇭

    Long-lived particles can manifest themselves at the LHC via "displaced vertices" - several charged tracks originating from a position separated from the proton interaction point by a macroscopic distance. Here we demonstrate a potential of the muon trackers at the CMS experiment for displaced vertex searches. We use heavy neutral leptons and Chern-Simons portal as two examples of long-lived particles for which the CMS muon tracker can provide essential information about their properties.

    hep-phhep-exPRD(2019)·28 citations
12. 12*

    The excited bottom-charmed mesons in a nonrelativistic quark model

    Qi Li🇨🇳 · Ming-Sheng Liu🇨🇳 · Long-Sheng Lu🇨🇳 · Qi-Fang Lü🇨🇳 · Long-Cheng Gui🇨🇳 · Xian-Hui Zhong🇨🇳

    Using the newly measured masses of $B_c(1S)$ and $B_c(2S)$ from the CMS Collaboration and the $1S$ hyperfine splitting determined from the lattice QCD as constrains, we calculate the $B_c$ mass spectrum up to the $6S$ multiplet with a nonrelativistic linear potential model. Furthermore, using the wave functions from this model we calculate the radiative transitions between the $B_c$ states within a constituent quark model. For the higher mass $B_c$ states lying above $DB$ threshold, we also evaluate the Okubo-Zweig-Iizuka (OZI) allowed two-body strong decays with the ${}^3{P}_0$ model. Our study indicates that besides there are large potentials for the observations of the low-lying $B_c$ states below the $DB$ threshold via their radiative transitions, some higher mass $B_c$ states, such as $B_c(2^3{P}_2)$, $B_c(2^3{D}_1)$, $B_c(3^3{D}_1)$, $B_c(4^3{P}_0)$, and the $1F$-wave $B_c$ states, might be first observed in their dominant strong decay channels $DB$, $D{B}^{\ast }$ or $D^{\ast }B$ at the LHC for their relatively narrow widths.

    hep-phhep-exPRD(2019)·78 citations
13. 13*

    Spectral function for overoccupied gluodynamics from classical lattice simulations

    K. Boguslavski🇦🇹 · A. Kurkela🇨🇭 · T. Lappi🇫🇮 · J. Peuron🇮🇹

    We study the spectral properties of an overoccupied gluonic system far from equilibrium. Using classical Yang-Mills simulations and linear response theory, we determine the statistical and spectral functions. We measure dispersion relations and damping rates of transversally and longitudinally polarized excitations in the gluonic plasma, and also study further structures in the spectral function.

    hep-phnucl-thActa Phys.Polon.B(2019)·1 citation
14. 14*

    Strong decays of double-charmed pseudoscalar and scalar $cc\overline{u}\overline{d}$ tetraquarks

    S. S. Agaev🇦🇿 · K. Azizi🇹🇷 · H. Sundu🇹🇷

    The strong decays of the pseudoscalar and scalar double-charmed tetraquarks $T_{cc;\overline{u}\overline{d}}^{+}$ and ${\tilde{T}}_{cc;\overline{u}\overline{d}}^{+}$ are investigated in the framework of the QCD sum rule method. The mass and coupling of these exotic four-quark mesons are calculated in the framework of the QCD two-point sum rule approach by taking into account vacuum condensates of the quark, gluon, and mixed local operators up to dimension 10. Our results for masses $m_T=(4130\pm 170)\mathrm{MeV}$ and $m_{\tilde{T}}=(3845\pm 175)\mathrm{MeV}$ demonstrate that these tetraquarks are strong-interaction unstable resonances and decay to conventional mesons through the channels $T_{cc;\overline{u}\overline{d}}^{+}\to D^{+}{D}^{\ast }(2007{)}^0,D^0{D}^{\ast }(2010{)}^{+}$ and ${\tilde{T}}_{cc;\overline{u}\overline{d}}^{+}\to D^{+}{D}^0$. Key quantities necessary to compute the partial width of these decay modes, i.e., the strong couplings of two $D$ mesons and a corresponding tetraquark $g_i,i=1,2$, and $G$ are extracted from the QCD three-point sum rules. The full width ${\Gamma }_T=(129.9\pm 23.5)\mathrm{MeV}$ demonstrates that the tetraquark $T_{cc;\overline{u}\overline{d}}^{+}$ is a broad resonance, whereas the scalar exotic meson with ${\Gamma }_{\tilde{T}}=(12.4\pm 3.1)\mathrm{MeV}$ can be classified as a relatively narrow state.

    hep-phhep-exhep-latPRD(2019)·30 citations
15. 15*

    Pentaquark and Tetraquark states

    Yan-Rui Liu🇨🇳 · Hua-Xing Chen🇨🇳 · Wei Chen🇨🇳 · Xiang Liu🇨🇳 · Shi-Lin Zhu🇨🇳

    The past seventeen years have witnessed tremendous progress on the experimental and theoretical explorations of the multiquark states. The hidden-charm and hidden-bottom multiquark systems were reviewed extensively in [Phys. Rept. 639 (2016) 1-121]. In this article, we shall update the experimental and theoretical efforts on the hidden heavy flavor multiquark systems in the past three years. Especially the LHCb collaboration not only confirmed the existence of the hidden-charm pentaquarks but also provided strong evidence of the molecular picture. Besides the well-known $XYZ$ and $P_c$ states, we shall discuss more interesting tetraquark and pentaquark systems either with one, two, three or even four heavy quarks. Some very intriguing states include the fully heavy exotic tetraquark states $QQ\bar{Q}\bar{Q}$ and doubly heavy tetraquark states $QQ\bar{q}\bar{q}$, where $Q$ is a heavy quark. The $QQ\bar{Q}\bar{Q}$ states may be produced at LHC while the $QQ\bar{q}\bar{q}$ system may be searched for at BelleII and LHCb. Moreover, we shall pay special attention to various theoretical schemes. We shall emphasize the model-independent predictions of various models which are truly/closely related to Quantum Chromodynamics (QCD). There have also accumulated many lattice QCD simulations through multiple channel scattering on the lattice in recent years, which provide deep insights into the underlying structure/dynamics of the $XYZ$ states. In terms of the recent $P_c$ states, the lattice simulations of the charmed baryon and anti-charmed meson scattering are badly needed. We shall also discuss some important states which may be searched for at BESIII, BelleII and LHCb in the coming years.

    hep-phhep-exhep-latnucl-thPPNP(2019)·914 citations
16. 16*

    The decay $h\to Z\gamma$ in the Standard-Model Effective Field Theory

    A. Dedes🇬🇷 · K. Suxho🇬🇷 · L. Trifyllis🇬🇷

    We calculate the $S$-matrix element for the Higgs boson decay to a $Z$-boson and a photon, $h\to Z\gamma$, at one-loop in the Standard-Model Effective Field Theory (SMEFT) framework and in linear $R_{\xi }$-gauges. Our SMEFT expansion includes all relevant operators up to dimension-6 considered in Warsaw basis without resorting to any flavour or CP-conservation assumptions. Within this approximation there are 23 dimension-6 operators affecting the amplitude, not including flavour and hermitian conjugation. The result for the on-shell $h\to Z\gamma$ amplitude is gauge invariant, renormalisation-scale invariant and gauge-fixing parameter independent. The calculated ratio of the SMEFT versus the SM expectation for the $h\to Z\gamma$ decay width is then written in a semi-numerical form which is useful for further comparisons with related processes. For example, the $h\to Z\gamma$ amplitude contains 16 operators in common with the $h\to \gamma \gamma$ amplitude and one can draw useful results about its feasibility at current and future LHC data.

    hep-phJHEP(2019)·52 citations
17. 17*

    Probing dark matter particles at CEPC

    Zuowei Liu🇨🇳 · Yong-Heng Xu🇨🇳 · Yu Zhang🇨🇳

    We investigate the capability of the future electron collider CEPC in probing the parameter space of several dark matter models, including millicharged dark matter models, $Z^{\prime }$ portal dark matter models, and effective field theory dark matter models. In our analysis, the monophoton final state is used as the primary channel to detect dark matter models at CEPC. To maximize the signal to background significance, we study the energy and angular distributions of the monophoton channel arising from dark matter models and from the standard model to design a set of detector cuts. For the $Z^{\prime }$ portal dark matter, we also analyze the $Z^{\prime }$ boson visible decay channel which is found to be complementary to the monophoton channel in certain parameter space. The CEPC reach in the parameter space of dark matter models is also put in comparison with Xenon1T. We find that CEPC has the unprecedented sensitivity to certain parameter space for the dark matter models considered; for example, CEPC can improve the limits on millicharge by one order of magnitude than previous collider experiments for $\mathcal{O}(1)-100$ GeV dark matter.

    hep-phastro-ph.COastro-ph.HEhep-exJHEP(2019)·40 citations
18. 18*

    Neutrino mass via linear seesaw, 331-model and Froggatt-Nielsen mechanism

    Katri Huitu🇫🇮 · Niko Koivunen🇫🇮 · Timo J. Kärkkäinen🇫🇮

    In this paper, we introduce an extension of the Standard Model, based on SU(3)${}_{\mathrm{C}}\times$SU(3)${}_{\mathrm{L}}\times$U(1)${}_X$ gauge symmetry (331-model). The 331-models traditionally explain the number of fermion familes in nature. In our model the Froggatt-Nielsen mechanism is incorporated into the 331-setting in a particularly economical fashion. The model utilizes the both the Froggatt-Nielsen and linear seesaw mechanisms to explain the observed fermion mass hierarchies and lightness of neutrinos. In our numerical analysis we found that a $\sim$ 50 TeV new physics scale is able to reproduce correctly all the fermion masses and mixing matrices, including neutrino masses, mass squared differences and mixing matrix.

    hep-ph3 citations
19. 19*

    Direct CP violation in multi-body $B$ decays with the $a_0^0(980)$--$f_0(980)$ mixing

    Chao Wang · Xian-Wei Kang🇨🇳 · Rui-Wu Wang · Xin-Heng Guo🇨🇳

    We predict that the $a_0^0(980)$-$f_0(980)$ mixing would lead to large CP violation. We calculate the localized direct CP asymmetry in the decays $B^{\pm }\to f_0(980)[a_0^0(980)]{\pi }^{\pm }\to {\pi }^{+}{\pi }^{-}{\pi }^{\pm }$ via the $a_0^0(980)$-$f_0(980)$ mixing mechanism based on the hypothetical $q\bar{q}$ structures of $a_0^0(980)$ and $f_0(980)$ in the QCD factorization. It is shown that there is a peak for CP violation, which could be as large as 58%, when the invariance mass of $\pi \pi$ is near the masses of $a_0^0(980)$ and $f_0(980)$. Since the CP asymmetry is sensitive to the $a_0^0(980)$-$f_0(980)$ mixing, measuring the CP violating parameter in the aforementioned decays could provide a new way to verify the existence of the $a_0^0(980)$-$f_0(980)$ mixing and be helpful in clarifying the configuration nature of the light scalar mesons.

    hep-phhep-exPRD(2019)·4 citations
20. 20*

    Radiative corrections to double-Dalitz decays revisited

    Pablo Sanchez-Puertas🇪🇸

    We revise the radiative corrections to double-Dalitz decays ($P\to \ell \bar{\ell }{\ell }^{\prime }{\bar{\ell }}^{\prime }$), completing the full next-to-leading order calculation in QED as compared to existing calculations. As a result, we find mild differences with respect to previous studies, that might be relevant for extracting information about the mesons transition form factors. The latter play an important role in determining the hadronic light-by-light contribution to the anomalous magnetic moment of the muon. Finally, we outline an ongoing extension of this work to the $e^{+}{e}^{-}\to e^{+}{e}^{-}P$ processes.

    hep-phPoS(2019)·0 citations
21. 21*

    Gravitational Atoms

    Niklas G. Nielsen🇩🇰 · Andrea Palessandro🇩🇰 · Martin S. Sloth🇩🇰

    Particles in a yet unexplored dark sector with sufficiently large mass and small gauge coupling may form purely gravitational atoms (quantum gravitational bound states) with a rich phenomenology. In particular, we investigate the possibility of having an observable signal of gravitational waves or ultra high energy cosmic rays from the decay of gravitational atoms. We show that if ordinary Einstein gravity holds up to the Planck scale, then, within the $\Lambda \text{CDM}$ model, the frequency of the gravitational wave signal produced by the decays is always higher than $10^{13}\text{Hz}$. An observable signal of gravitational waves with smaller frequency from such decays, in addition to probing near Planckian dark physics, would also imply a departure from Einstein gravity near the Planck scale or an early epoch of non-standard cosmology. As an example, we consider an early universe cosmology with a matter-dominated phase, violating our assumption that the universe is radiation dominated after reheating, which gives a signal in an interesting frequency range for near Planckian bound states. We also show how gravitational atoms arise in the minimal PIDM scenario and compute their gravitational wave signature.

    hep-phastro-ph.COhep-thPRD(2019)·17 citations
22. 22*

    Gas-rich dwarf galaxies as a new probe of dark matter interactions with ordinary matter

    Digvijay Wadekar🇺🇸 · Glennys R. Farrar🇺🇸

    We use observations of gas-rich dwarf galaxies to derive constraints on dark matter scattering with ordinary matter. We require that heating/cooling due to DM interacting with gas in the Leo T dwarf galaxy not exceed the ultra-low radiative cooling rate of the gas. This enables us to set $(i)$ stronger bounds than all the previous literature on ultra-light hidden photon DM for nearly all of the mass range $10^{-23}\lesssim m_{\mathrm{DM}}\lesssim 10^{-10}$ eV, $(ii)$ limits on sub-GeV millicharged DM which add to the constraints on the recent EDGES 21cm absorption anomaly, and $(iii)$ constraints on DM-baryon interactions directly at low relative velocities $v_{\mathrm{rel}}\sim 17$ km/s. Our study opens a new direction at using observations of gas-rich dwarf galaxies from previous, current and upcoming optical and 21cm surveys to probe physics beyond the standard model.

    hep-phastro-ph.GAPRD(2021)·113 citations
23. 23*

    Comment on the paper "Calorimetric Dark Matter Detection with Galactic Center Gas Clouds"

    Glennys R. Farrar🇺🇸 · Felix J. Lockman🇺🇸 · N. M. McClure-Griffiths🇦🇺 · Digvijay Wadekar🇺🇸

    The paper "Calorimetric Dark Matter Detection with Galactic Center Gas Clouds" (Bhoonah et al. 2018) aims to derive limits on dark matter interactions by demanding that heat transfer due to DM interactions is less than that by astrophysical cooling, using clouds in the hot, high-velocity nuclear outflow wind of the Milky Way ($T_{wind}\sim 10^{6-7}$ K, $V_{wind}\sim$ 330 km/s). We argue that clouds in such an extreme environment cannot be assumed to be stable over the long timescales associated with their radiative cooling rates. Furthermore, Bhoonah et al. (2018) uses incorrect parameters for their clouds.

    hep-phastro-ph.GAPRL(2020)·18 citations
24. 24*

    Mirror Dirac leptogenesis

    Kevin Earl🇨🇦 · Chee Sheng Fong🇧🇷 · Thomas Gregoire🇨🇦 · Alberto Tonero🇨🇦

    We consider a mirror world scenario, in which light Dirac neutrinos are generated from a seesaw mechanism and leptogenesis occurs at high scale without violating lepton number. After leptogenesis, the conservation laws of the theory imply the visible baryon-minus-lepton asymmetry to be equal to the mirror baryon-minus-lepton asymmetry. We extend previous work by presenting a detailed study of this Dirac leptogenesis mechanism by constructing the full set of Boltzmann Equations for both cases of unflavored and flavored regimes. We show that $Z_2$ breaking and lepton/mirror lepton flavor effects can be exploited to enhance the final baryon-minus-lepton asymmetry in our world by several orders of magnitude.

    hep-phJCAP(2020)·21 citations
25. 25*

    Dark Energy, $H_0$ and Weak Gravity Conjecture

    Nemanja Kaloper🇺🇸

    We point out that the physics at the extreme IR---cosmology---might provide tests of the physics of the extreme UV---the Weak Gravity Conjecture. The current discrepancies in the determination of $H_0$ may hint at a modification of $\Lambda$CDM. An extension which may fit better comprises of an early contribution to dark energy which `decays' into relativistic matter. On the other hand the discourse on WGC to date suggests that fields which support cosmic acceleration may produce relativistic matter after they traverse a $\sim$ Planckian distance in field space. We explain how this offers a simple realization of the requisite cosmic phenomenology. Thus if the resolution of $H_0$ discrepancies is really early dark energy that ends with a shower of relativistic matter and the current ideas on WGC are indicative, this may be a rare opportunity to link the two extreme limits of quantum field theory.

    ↳ hep-thastro-ph.COgr-qchep-phInt.J.Mod.Phys.D(2019)·69 citations
26. 26*

    A hint of matter underdensity at low $z$?

    Eoin Ó Colgáin🇰🇷

    The $\Lambda$CDM cosmological model provides to first approximation a good description of the universe, but various tensions with data, most notably Hubble tension, persist. In this work we confront $\Lambda$CDM with the Pantheon Type Ia supernovae dataset and perform a two-parameter fit of the distance modulus for a running cut-off $z_{\text{max}}$. We observe that in a window between $z_{\text{max}}\approx 0.1$ and $z_{\text{max}}\approx 0.16$ there is a 1 - 2 $\sigma$ discrepancy with the Planck value ${\omega }_m=0.315\pm 0.007$, which points to a potential matter underdensity. For high-energy theorists, the analysis appears to support the de Sitter Swampland conjecture.

    ↳ astro-ph.COgr-qchep-phhep-thJCAP(2019)·46 citations
27. 27*

    Testing the Gravitational Weak Equivalence Principle in the Standard-Model Extension with Binary Pulsars

    Lijing Shao🇨🇳 · Quentin G. Bailey🇺🇸

    The Standard-Model Extension provides a framework to systematically investigate possible violation of the Lorentz symmetry. Concerning gravity, the linearized version was extensively examined. We here cast the first set of experimental bounds on the nonlinear terms in the field equation from the anisotropic cubic curvature couplings. These terms introduce body-dependent accelerations for self-gravitating objects, thus violating the gravitational weak equivalence principle (GWEP). Novel phenomena, that are absent in the linearized gravity, remain experimentally unexplored. We constrain them with precise binary-orbit measurements from pulsar timing, wherein the high density and large compactness of neutron stars are crucial for the test. It is the first study that seeks GWEP-violating signals in a fully anisotropic framework with Lorentz violation.

    ↳ gr-qcastro-ph.HEhep-phPRD(2019)·27 citations
28. 28*

    Constraints on Scalar and Tensor spectra from $N_{eff}$

    Ido Ben-Dayan🇮🇱 · Brian Keating🇺🇸 · David Leon🇺🇸 · Ira Wolfson🇮🇱

    At the linear level, the gravitational wave (GW) spectrum predicted by inflation, and many of its alternatives, can have arbitrarily small amplitude and consequently an unconstrained tilt. However, at second order, tensor fluctuations are sourced by scalar fluctuations that have been measured in the cosmic microwave background (CMB). These second order fluctuations generically produce a minimum amount of tensor perturbations corresponding to a tensor-to-scalar ratio of $r\sim 10^{-6}$. Inverting this relationship yields a bound on the tensor tilt sourced by scalar fluctuations. Since this induced GW spectrum depends on the scalar spectrum, we derive a new indirect bound that involves \textit{all scales} of the scalar spectrum based on CMB observations. This bound comes from the constraint on the number of effective relativistic degrees of freedom, $N_{eff}$. We estimate the bound using current data, and the improvements expected by future CMB experiment. The bound forces the running and running of running to conform to standard slow-roll predictions of $\alpha ,\beta \lesssim (n_s-1{)}^2$, improving on current CMB measurements by an order of magnitude. This bound has further implications for the possibility of primordial black holes as dark matter candidates. Performing a likelihood analysis including this new constraint, we find that positive $\alpha$ and/or $\beta$ are disfavored at least at $1\sigma$. Finally, using bounds on the fractional energy density of gravitational waves today obtained by LIGO and the Pulsar Timing Array, we obtain a bound on the primordial scalar spectrum on these scales and give forecast for future measurements.

    ↳ astro-ph.COhep-phhep-thJCAP(2019)·73 citations
29. 29*

    Measuring the Neutron Distribution from Coherent Elastic Neutrino Nucleus Scattering

    E. Ciuffoli🇨🇳

    Last year the COHERENT collaboration was able to measure for the first time the Coherent Elastic Neutrino Nucleus Scattering (CE$\nu$NS). Neutrinos within the right energy range can be produced in large quantities at accelerator facilities via pion Decay At Rest ($\pi$DAR) and used to measure CE$\nu$NS. This new channel opens several, interesting possibilities: studying the CE$\nu$NS spectrum it will be possible, for example, to search for Physics Beyond the Standard Model, looking for deviations from the predictions of the electroweak theory; it can also give important inputs for the understanding of core collapse supernovas, where neutrino-nucleus interactions and, more generally, collective neutrino behavior play a crucial role. Using CE$\nu$NS it is also possible to measure precisely the electroweak form factor for a large number of different nuclei, extracting information on the neutron distribution inside the nucleus as well. In this presentation I will focus on the last aspect: I will calculated the precision that can be achieved in such kind of experiment, investigating in particular the effects of the low-energy threshold and the systematic errors on the quenching factor. The expected precision will be calculated using the Helm model and also with a model-independent approach.

    ↳ hep-exhep-phphysics.ins-det1 citation
30. 30*

    Heterotic Stringy Corrections to Metrics of Toroidal Orbifolds and Their Resolutions

    Pompey Leung🇯🇵 · Hajime Otsuka🇯🇵

    We explicitly analyse $O({\alpha }^{\prime })$ corrections to heterotic supergravity on toroidal orbifolds and their resolutions, which play important roles in string phenomenology as well as moduli stabilisation. Using a conformal factor ansatz that is valid only for four dimensional geometries, we obtain a closed expression for the $O({\alpha }^{\prime })$ metric corrections in the case of several orbifold limits of K3, namely $T^4/{\mathbb{Z}}_n$ where $n=2,3,4,6$. However, we find that non-standard embedding requires the inclusion of five-branes on such orbifolds. We also numerically investigate the behaviour around orbifold fixed points by considering the metric correction on the resolution of a ${\mathbb{C}}^2/{\mathbb{Z}}_2$ singularity. In this case, a non-trivial conformal factor can be obtained in non-standard embedding even without five-branes. In the same manner, we generalise our analysis to study metric corrections on $T^6/{\mathbb{Z}}_3$ and its resolution described by a complex line bundle over ${\mathbb{CP}}^2$. Further prospects of utilising these $O({\alpha }^{\prime })$ corrected metrics as a novel approach in obtaining realistic or semi-realistic Yukawa couplings are discussed.

    ↳ hep-thhep-phPRD(2019)·6 citations
31. 31*

    Longitudinal spin polarization in a thermal model

    Wojciech Florkowski🇵🇱 · Avdhesh Kumar🇵🇱 · Radoslaw Ryblewski🇵🇱 · Aleksas Mazeliauskas🇨🇭

    We use a thermal model with single freeze-out to determine longitudinal polarization of $\Lambda$ hyperons emitted from a hot and rotating hadronic medium. We consider the top RHIC energies and use the model parameters determined in the previous analyses of particle spectra and elliptic flow. Using a direct connection between the spin polarization tensor and thermal vorticity, we reproduce earlier results which indicate a quadrupole structure of the longitudinal component of the polarization three-vector with an opposite sign compared to that found in the experiment. We further use only the spatial components of the thermal vorticity in the laboratory system to define polarization and show that this leads to the correct sign and magnitude of the quadrupole structure. This procedure resembles a non-relativistic connection between the polarization three-vector and vorticity employed in other works. In general, our results bring further evidence that the spin polarization dynamics in heavy-ion collisions may be not directly related to the thermal vorticity. The additional material explains the construction of the hydrodynamicaly consistent gradients of fluid velocity and temperature in thermal models with the help of the perfect-fluid equations of motion.

    ↳ nucl-thhep-phPRC(2019)·107 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.